@JonCarter Not recommended Jon, largely due to cold flow migrating away from the pressure of the bolt or screw. Ferrules are precisely sized by wire gauge, keep all the strands contained from escaping and protect the strands from damage; correctly sized and crimped Sta-kon / crimp-on pin terminals do likewise. I believe @STEVETERRY was in agreement with me but felt few contractors would source or employ correctly sized ferrules or Sta-kon pin terminals. Tinning stranded, and fine stranded, conductors is a fine idea prior to soldering in place but NOT when they're about to have a bolt screwed down on them leaving them free to migrate away from the point of applied pressure.
As much as I hate to admit it, I've landed terminals this way too. Not only that, but they're at the sockets of my VL500's which probably reach a temperature close enough to reflow solder! They haven't failed yet, but I've been meaning to re-terminate these for a few *cough* years now...